In modern transmission systems, such as the ISDN (Integrated Services Digital Network) system or the wide-band ISDN (B-ISDN), to transmit data streams, the transmission properties of established transmission path must be checked for the occurrence of bit errors. Bit errors caused by external interference effects acting on the transmission path corrupt the digital data stream originally sent out and, thus, interfere with information transmission.
The object of the present invention is to provide a process for determining the nature of an interference that causes bit errors with regard to its stochastic or deterministic character. When the bit-error type is known, the origin and/or the cause of the bit errors can be searched for efficiently.